Pinus juarezensis x monophylla hybrids
Photos 1 to 3 were taken at a stand containing pure and hybrid P. juarezensis, located at latitude 33.55932922°N, longitude 116.6045977°W, about a mile south of the junction of CA 371 and CA 74, on the south flank of the Mt. San Jacinto massif. The surrounding vegetation is chaparral. Photo 4 was taken at the "P. quadrifolia" stand at the Rancho Santa Ana Botanical Garden, Claremont, California.
Photo 1 shows a hybrid bearing predominantly 2-needled fascicles. Although many hybrids are 4-needled, the presence of predominantly 2-needled trees as well as 1-, 4- and 5- needled trees in a stand supports a hybridization hypothesis. I have yet to find a predominantly 3-needled tree.
Photo 2 shows the bark of the hybrid tree shown above. Compare to THIS photo of P. monophylla bark; I find them very similar.
Photo 3 shows the cone from the hybrid tree. Compare to this P. juarezensis cone and this P. monophylla cone. P. monophylla cones seem to be wider and flatter, and overall larger, compared to P. juarezensis cones; the hybrid cone is closer to P. juarezensis than to P. monophylla.
Photo 4 shows a hybrid's 4-needle fascicle. Note how the needles remain together for the first year, functioning (as far as photosynthesis and gas exchange are concerned) as a pseudo-single leaf. Is the persistence of this trait the evolutionary origin of P. monophylla?
Last Modified 2011-05-22